Mating success of the endemic Des Murs' Wiretail (Sylviorthorhynchus desmursii, Furnariidae) in fragmented Chilean rainforests

Abstract

We studied the effects of fragment size, vegetation structure and presence of habitat corridors on the reproductive success of the Des Murs' Wiretail (Sylviorthorhynchus desmursii Des Murs, Furnariidae), a small (10 g) understorey bird, endemic to South American forests. In a rural landscape of Chiloe Island, southern Chile (42 degrees S; 70 degrees W), we determined the mating and nesting success of wiretails in 28 territories distributed in seven small (1-20 ha) and two large (> 300 ha) forest fragments during the 1997-1998 breeding season. Wiretails inhabited dense bamboo thickets in the understorey of forest patches, dense shrublands covering old fields, and dense early successional forest vegetation. Wiretails avoided open pastures. Reproductive success depended solely on the probability of finding mates, and the main factor affecting mating success was the presence of corridors. Mated individuals occupied 72% of the territories in forest patches < 20 ha connected by corridors, 73% of the territories in large (> 300 ha) fragments, but only 20% of territories in isolated fragments surrounded by pastures. Because of the rapid expansion of pastures in southern Chile, the conservation of wiretails and other understorey birds will depend on the maintenance of travel corridors with dense understorey vegetation between forest fragments.